Compensating terminal for electric furnaces.



PATENTED SEPT. 20, 1904 H. N; POTTER. UOMPENSATING TERMINAL FOR ELECTRIC FURNACES.

N0 MODEL.

APPLICATION FILED AUG. 6. 1903.

[law/afar 1 aw/4% RE UNITED STATES Patented September 20, 1904.

PATENT OFFICE.

HENRY NOEL POTTER, OF NEW ROCHELLE, NEW YORK, ASSIGNOR TO GEORGE WESTINGHOUSE, OF PITTSBURG, PENNSYLVANIA.

COMPENSATING TERMINAL FOR ELECTRIC FURNACES.

SPECIFICATION forming part of Letters Patent No. 770,312, dated September 20, 1904.

Application filed August 6, 1903.

To all whom, it ntay concern.-

Be it known that I, HENRY NOEL POTTER, a citizen of the United States, and a resident of New Rochelle, in the county of IVestchester and State of New York, have invented certain new and useful Improvements in Compensating Terminals for Electric Furnaces, of which the following is a specification.

My invention relates to improvements in terminals for electric furnaces where the parts constituting the terminals have different degrees of expansibility under the influence of heat. The same principle might be applied to any terminals wherein conducting substances of different character are brought into contact and are subjected to varying temperatures. The electric furnace is selected as a good example, inasmuch as the furnace-body is likely to be of graphite or some other form of carbon, while the cooperating terminals which conduct electric current to the furnacebody are generally of metal having a different degree of expansibility under the heat of the furnace.

The object of the present invention is to provide a compensating terminal by the use of which the different expansion of the parts constituting the terminal are prevented from resulting in disturbing variations of pressure. As furnace terminals are now constituted without the compensation provided by this invention, the different elements of the terminal may become distorted by the action of heat, whereby the resistance at the terminal is greatly increased and a loss of energy ensues.

In the accompanying drawing I have shown a section of a furnace-terminal in which the furnace itself is of tubular shape and is of some form of carbon, such as graphite.

In a typical form of furnace I make the body or core of the furnace conical at the ends and may combine therewith a terminal of the same material. The means of connection with the external circuit may be, however, and generally are a suitably-shaped piece of metal, such as copper or brass. Naturally the details may be varied under varying conditions or to suit various needs or purposes.

Referring to the drawing, 1 is a core or fur- Serial No. 168,454. (No model.)

nace-body of graphite or other form of carbon, and 2 is a terminal of similar material making good mechanical and electrical contact therewith. The part 2 is provided with a flange or enlargement 6, and its outer end makes contact with a terminal 3 of copper, brass, or other material. The parts 2 and 8 are joined, as shown, by means of bolts 4 4, which may be of steel or iron, suitable washers 5 5 being interposed to assist in making the connection.

The essential thing in connection with apparatus of this sort in order to make the terminal what I call a compensating terminal is that the bolts 4 4 should have an expansion coeflicient intermediate between that of the terminal 2 and terminal 8. Then by properly dimensioning the parts 2 and 3 the terminal can be so constructed as to be self-compensating-that is to say, the reactions of the parts under the influence of heat will just balance each other-so that the pressure between the parts 2 and 3 will remain practically constant under actual variationsof temperature. The following will serve as a concrete example of such a compensating terminal.

Assuming that the terminal will be raised to 800 Centigrade by the operation of the furnace and that the flange 6 is ten centimeters in thickness at Zero degrees, if the coefficient of expansion of graphite between zero and 300 is .2691 per cent. the said flange 6 will be 10.026913 centimeters in thickness at 300 Assuming that the coefficient of copper between zero and 300 is .57105 per cent. and that of iron is .42405 per cent, then it may readily be calculated that if the terminal 3 be of copper and be 10.47 centimeters in length then the expansion of the flange 6 plus that of the terminal 3 will be just equal to the expansion of the bolts 4 4 throughout that portion of their extent in which their expansion is capable of affecting the pressure between the parts 6 and 3.

It will be understood, of course, that such portions of the bolts 4 4 as are covered by nuts or Washers composed of the same material as the bolts themselves will not be active in the sense meant.

I claim as my invention constant pressure between the carbon body A terminal for electric-resistance furnaces, and the said contact throughout the range of consisting of a body of carbon, a metal contemperature to Which the terminal is exposed. tact shaped to conform to the said carbon body Signed at New York, in the county of N eW 5 and clamped against said body by a bolt or York and State of New York, this 4th day of 5 bolts, said contact being composed of a metal August, A. D. 1903.

having a higher thermic expansion coefficient HENRY NOEL POTTER. than that of the metal composing the bolt, and l/Vitnesses: so proportioned in thickness relative to the HERMAN SIEGEL,

I length of the bolt as to maintain practically WM. H. CAPEL. 

